1. Field of the Invention
This invention relates to a dry, initially non-tacky, heat expansible sealant and baffle composition which is formable into a desired shape so that upon insertion of a sealant product of predetermined shape into a cavity such as the hollow post structure of an automobile or similar vehicle, followed by heat induced expansion thereof, it serves as a highly effective sealant and acoustic baffle within that cavity.
In particular, the invention concerns a heat expansible sealant and baffle composition which after being formed into a desired configuration is adapted to be placed within a vehicle post or other body cavity in a position such that when the vehicle body is subjected to a primer and/or paint baking operation or other process which elevates the temperature of the environment surrounding the vehicle body, the shaped sealant and baffle product expands to an extent that the expanded component serves to attenuate annoying sounds that would otherwise pass through the cavity. The expanded product also functions to seal the cavity and thereby prevent infiltration of moisture, dust, air, other undesirable fluids, and sound.
2. Description of the Prior Art
During the fabrication of automobiles, trucks and similar over-the-road vehicles, many body components present cavities which require sealing to prevent ingress of moisture and contaminants which can cause corrosion of the body parts. This is especially true with respect to unibody structures in which a heavy frame is replaced with a structurally designed space frame that inherently presents a number of moisture and contaminant collecting cavities. These cavities also serve as passages which attenuate noise and other sounds transmitted therethrough during normal use of the vehicle. For example, the upright post structure of a vehicle's body defining a portion of a respective window opening presents an elongated passage or cavity which can collect moisture and contaminants and also transmit annoying sounds unless the passage or cavity is at least partially filled with a sealant material that blocks entrance of moisture and debris, and that also serves as a baffle for muting sounds that would otherwise be transmitted along the length of the passage or cavity. There are other irregular cavities in a vehicle body which desirably are sealed to prevent moisture and contaminants from entering that area and being conveyed to other parts of the interior of the vehicle body.
Many attempts have been made to seal these cavities, including spraying of a sealant into the cavity, introduction of foam products into such cavities, and use of fiberglass matting and the like. These past efforts have not been entirely satisfactory because of the inefficiency of the sealing and baffling methods, the relatively high cost of the sealing process, and the fact that erratic sealing has resulted in many instances.
Foaming in place has not been totally satisfactory because of the difficulty in controlling where the foam travels upon introduction of the foam into a vehicle body cavity or the like, and the fact that more foam than is actually needed is usually introduced into the body cavity to provide some degree of redundancy in preventing entry of moisture into the cavity during use of the vehicle. Furthermore, foams have a finite life insofar as flexibility is concerned before becoming rigid, thus limiting the time available during which the foam may be introduced into the vehicle cavity. In addition, if the interior surface of the cavity had a somewhat oily surface, the foams would not adequately adhere to that surface and provide an effective seal.
Other types of foam or foamable products are tacky in nature and thus cannot readily be positioned at the exact required disposition in the selected cavity. Certain sealant and baffling materials also are sensitive to the elevated temperature conditions to which a vehicle body may be subjected during fabrication of a vehicle thus causing disruption of the sealant and sound attenuating properties of the sealant.